Marantz is very easy for access, with 'clean' PCB and neat wires / ribbon cables. It is the best choice if you are going to remove the PCB and mechanism a number of times. The PCB quality is very high and suitable for many soldering / desoldering attempts.

Rotel has better chipset and higher quality components, but it is messy inside, however very good!

Arcam I have not modified - I think it's too plasticky and overpriced and I refuse to touch it! (but I had a look inside and wondered how they manage to sell it at the price????!!!!)

Extreme Boky: thanks for the insight. I'm kind of leaning towards the rotel because of component quality and the machines are a little younger than the 63se. I say that regards to longevity not that the newer model would necessarily sound better.

I'll see what happens in the next couple of days with the bidding though.

I have a Marantz CD63 SE I bought new about 5 years ago. I've been very happy with it.

Rather than go the upgrade and mod route... I found an Adcom GDA 700 DAC with balanced outputs that soulds fantastic! An EASY 2x improvement in sound quality in nearly every dimension. I bought the Adcom GDA700 on eBay for less than the costs of mods for the cd63SE.

I've heard them all.
The Arcam is slightly better than the Rotel in original form.
But I think that the Rotel has more potential if you are going to tweak.
The Rotel 971 is a much better player than the 951.
Ultimately, in my scale, and in original form, both the 7SE and the 951 are very bad players.
I know, you can read otherwise in the mags.
Pick the Marantz, don't look back.